Does the Full Moon Really Influence Human Behavior?

For centuries, strange or chaotic behavior has often been blamed on one thing: the full moon.

“It must be a full moon,” people say after witnessing reckless driving, odd public outbursts, or unusually tense interactions. The idea isn’t new. As far back as the first century, thinkers like Aristotle and Roman historian Pliny the Elder suggested that the moon could trigger madness in humans. Even the word lunatic comes from the Latin lunaticus, meaning “moonstruck” or “of the moon.”

Despite how deeply rooted this belief is, modern science has struggled to find evidence that lunar phases directly influence human behavior. So why does the superstition persist?

Where the Belief Came From

Ancient philosophers believed the moon affected people for the same reason it affects tides. Aristotle and Pliny argued that because the human brain contains moisture, it could be influenced by lunar forces just as oceans are. They believed the full moon could provoke insanity, seizures, or irrational behavior.

This idea didn’t disappear with ancient history. In the late 20th century, psychiatrist Arnold Lieber revisited the theory in his books The Lunar Effect and How the Moon Affects You. Lieber proposed that since the human body is roughly 70 percent water, lunar gravity might create biological “tides,” increasing rates of violence, suicide, psychiatric emergencies, and fatal accidents during full moons.

While the theory sounded compelling, scientists were quick to challenge it. Researchers pointed out that Earth’s gravitational pull is thousands of times stronger than the moon’s, and the moon’s influence on a human body would be no more than the weight of a flea. While the moon can move massive oceans, its effect on the water inside the human body is essentially negligible.

Astronomers, physicists, and psychologists largely agree: lunar phases do not cause changes in human behavior.

What the Research Shows

In 1985, researchers reviewed 37 separate studies examining links between lunar cycles and suicides, crimes, psychiatric emergencies, and crisis calls. The conclusion was clear—there was no meaningful connection.

More recent studies support those findings. Researchers have found no correlation between full moons and psychiatric admissions, hospital visits, or aggressive behavior. One study from Finland even reported fewer homicides during full moons, not more…